Method of forming a composite tubular structure

ABSTRACT

A method of forming a composite tubular structure, such as a drive shaft, composed of a tubular member formed of fiber reinforced resin and having metal yokes secured to the ends of the tubular member. Each yoke includes a cylindrical sleeve portion bonded in overlapping relation to the respective end of the tubular member. A plurality of longitudinally extending ribs or bosses are formed on each sleeve portion and are received in slots provided in the respective end of the tubular member. Windings of a fibrous material impregnated with a thermosetting resin can be applied over the joint between the tubular member and each sleeve portion. With this construction the torsional load is transmitted through the ribs and slots rather than through an adhesive bonded interface between the members.

This is a division of application Ser. No. 075,234, filed July 17,1987,now U.S. Pat. No. 4,792,320, issued Dec. 20, 1988, which is acontinuation of application Ser. No. 777,191, filed Sept. 18, 1985, andnow abandoned.

BACKGROUND OF THE INVENTION

Traditionally, vehicle drive shafts have been formed of a steel tubehaving a high flexural modulus with a forged yoke welded to each end ofthe steel tube. With both the tube and the yokes formed of steel thedrive shaft is a relatively heavy structure.

At certain rotational speeds, a drive shaft can become dynamicallyunstable. The critical speed at which the instability occurs isgenerally proportional to the flexural modulus of the shaft and itsmoment of inertia and generally inversely proportional to the weight ofthe shaft and its length. To maintain an acceptably high critical speedwith a tubular steel drive shaft, the drive shaft in many instances isformed of short multiple sections and shaft support bearings areutilized along the length of the drive shaft which act to rotationallysupport the shaft sections.

Recently there has been considerable activity in the development ofcomposite drive shafts which are composed of a fiber reinforced resintube or shaft and light weight metal, such as aluminum, yokes. Thecomposite drive shaft achieves a substantial weight reduction ascompared to a steel drive shaft and due to the lighter weight, a onepiece composite shaft can replace the multi-section steel shafts, withthe resultant elimination of the shaft support bearings which areutilized with a multi-section steel shaft.

However, a problem in the production of a composite drive shaft has beenthe lack of an adequate connection between the fiber reinforced resintubular member and the yokes. In one approach to providing an adequateconnection between the tube or shaft and the yokes, the ends of thetube, which surround the sleeve portion of the yoke, are connected tothe sleeve portion by rivets. In another approach, as shown in U.S. Pat.No. 4,279,275, the sleeve portion of the yoke is provided with aplurality of longitudinally extending grooves and the resin impregnatedfibrous material, when producing the tubular member, is woundcircumferentially over the grooves to provide an improved mechanicalconnection between the tube and the yokes.

In the U.S. Pat. No. 4,358,284 the sleeve portion of the yoke isprovided with circumferential extending grooves or threads and thefibrous material is wound in the grooves to provide an improvedattachment, while in U.S. Pat. No. 4,380,443 a plurality of angularlyextending pins are employed to interconnect the wound tube with thesleeve portion of the yoke.

U.S. Pat. No. 4,248,062 proposes to increase the bond between the woundtube and the sleeve portion of the yoke by employing a specific windingpattern including longitudinal helical and circumferential windings.

SUMMARY OF THE INVENTION

The invention is directed to a method of forming a composite tubularstructure, such as a drive shaft having an improved attachment betweenthe fiber reinforced resin tubular member or shaft and the metal yokes.In accordance with the invention, the sleeve portion of each yoke isprovided with a plurality of longitudinally extending raised ribs orbosses which are received in slots formed in the respective ends of thefiber reinforced resin tubular member. Windings of a fibrous materialimpregnated with the thermosetting resin can be applied over the jointbetween the yokes and the tubular member. With this construction thetorsional load is transmitted through the ribs and slots rather thanthrough an adhesive bonded interface between the tubular member and theyokes.

In a modified form of the invention, the portion of the yoke sleeveextending between the bases of adjacent ribs is formed with a groovethat extends at acute angle to the axis of the yoke. The end portions ofthe tubular member located between adjacent slots define flexibletongues, and the end of each tongue is bent inwardly and received withinone of the grooves in the sleeve portion of the yoke. An adhesive bondis employed to secure the tips of the tongues within the grooves, aswell as to bond the contiguous portions of the tubular member to thesleeve of the yoke.

The invention provides an improved mechanical connection between thefiber reinforced resin tubular member or shaft and the yokes in whichthe torsional load is transmitted through the ribs and slots.

The composite drive shaft of the invention has a substantially reducedweight over a conventional steel drive shaft and reduces operationalnoise and vibration.

The composite drive shaft of the invention can be used for relativelylong drive shafts and eliminates the need for shaft support bearingswhich are required in multi-section steel drive shafts. Due to thelesser weight, the drive shaft produces less stress on the supportingbearings.

By use of the fiber reinforced resin tubular member along with forgedaluminum yokes, the drive shaft is corrosion resistant.

Other objects and advantages will appear in the course of the followingdescription.

DESCRIPTION OF THE DRAWINGS

The drawings illustrate the best mode presently contemplated of carryingout the invention.

In the drawings:

FIG. 1 is a side elevation of the composite drive shaft of the inventionwith parts broken away in section;

FIG. 2 is an exploded perspective view showing an end of the fiberreinforced resin tubular member and the yoke;

FIG. 3 is an exploded perspective view of a modified form of theinvention showing the ends of the tubular member and the yoke;

FIG. 4 is a longitudinal section of the connected members as illustratedin FIG. 3; and

FIG. 5 is a transverse section taken along line 5--5 of FIG. 4.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENT

FIG. 1 illustrates a composite drive shaft composed of a fiberreinforced resin shaft or tubular member 1 and a pair of metal yokes 2,formed of aluminum or the like, each of which is connected to an end ofthe tubular member 1.

Tubular member 1 is formed of a fibrous material such as glass fibers,or a combination of glass and graphite fibers, which are wound in apattern to provide the desired mechanical properties in the tubularmember. A combination of different winding patterns can be used, such assubstantially circumferential windings, helical windings andsubstantially longitudinal windings. The particular winding pattern andfibrous material employed in forming tubular member 1 is conventionaland in itself forms no part of the invention.

The fibrous material in tubular member 1 is bonded together by a curedthermosetting resin, such as an epoxy or polyester resin.

As best illustrated in FIG. 2, each yoke 2 is provided with a generallycylindrical sleeve portion 3 and a plurality of longitudinal raised ribsor bosses 4 are formed on the outer surface of the sleeve 3. As shown,four ribs 4 are utilized, but depending upon the particular application,one or more such ribs can be employed. Each rib is provided with agenerally curved or rounded outer end 5 as shown in FIG. 2.

As shown in FIG. 2, the ends of the tubular member 1 are provided withlongitudinal slots 6 which receive the ribs 4 on yoke 2. Each slot 6 isbordered by a pair of generally parallel walls 7 and a generally curvedor rounded base 8 which engages the rounded end 5 of the respective rib4. When tubular member 1 is applied over the sleeve 3, the ends 5 ofribs 4 bottom out against the bases 8 of slots 6 so that the end of thetubular member 1 is spaced out of contact with the shoulder 9 on theouter surface of yoke 2.

As an alternate construction, the ribs 4 can be formed on the innersurface of the sleeve 3, and the sleeve inserted over the tubular member1, so that the ribs are received in slots 6.

The contiguous surfaces of tubular member 1 and yokes 2 are bondedtogether, preferably by a thermosetting resin or an adhesive system.

To provide additional attachment between tubular member 1 and each yoke2, a fibrous material impregnated with a thermosetting resin can bewound around the outer surface of tubular member 1 and yoke 2 and acrossthe joint therebetween, as indicated by 10. The outer surfaces of ribs 4are substantially flush with the outer surface of the tubular member 1so that the resulting windings 10 will have a smooth outer surface orcontour. Alternately, a metal clamping band can be clamped over thejoint in place of the fibrous windings 10.

Each yoke 2 is provided with an axial bore which is normally enclosed bya plug 11. During the application of the windings 10, the compositestructure, including tubular member 1 and yokes 2, can be supported by acentral shaft that extends through the axial openings in yokes 2. Theshaft serves to properly align the two yokes 2 and tubular member 1during winding of the layer 10. After the windings have been applied,the shaft is removed from the composite structure and the axial boresare closed by the plugs 11.

FIGS. 3-5 illustrate a modified form of the invention in which thecomposite drive shaft includes a fiber reinforced resin shaft or tubularmember 12 and a pair of metal yokes 13. The cylindrical sleeve portion14 of each yoke 13 is formed with a plurality of longitudinallyextending raised ribs or bosses 15. As illustrated in FIG. 5, sleeveportion 14 includes six ribs 15 but it is contemplated that any numberof ribs can be utilized.

Each rib 15 is bordered by a pair of angularly extending sides 16 whichare connected together by a generally square end 17. As best illustratedin FIG. 4, the portions of sleeve 14 extending between the bases ofadjacent ribs 15 are formed with grooves 18 which extend at an acuteangle of about 10° to 20° with respect to the axis of sleeve 14.

As best shown in FIG. 3 each end of tubular member 12 is provided with aplurality of tongues 19 which border slots 20. Tongues 19 taper orconverge inwardly, as illustrated in FIG. 3, and are received in thespaces between ribs 15 on sleeve 14. The tongues 19 are relativelyflexible and the tips 21 of the tongues are bent or deformed inwardlyand are received within the angular grooves 18 in sleeve 14. In thisconstruction, the bases of slots 20 bottom out against the ends 17 ofribs 15 and the contiguous surfaces of the tubular member 12 and sleeve14 are bonded together by an adhesive such as a thermosetting resin.Bonding of the bent ends 21 of tongues 19 within grooves 18 serves toenhance the connection between the tubular member 12 and yokes 13.

As in the case of the first embodiment, windings 22 of a fibrousmaterial impregnated with a thermosetting resin can be applied over theouter surface of the tubular member 12 and yokes 13 to bridge the jointbetween the members.

The invention provides an improved mechanical interlock between thefiber reinforced resin tubular member or shaft and the metal yokes inwhich the torsional load is transmitted between the ribs and slotsrather than through an adhesive bonded interface between the members.

The composite drive shaft has a substantially reduced weight over aconventional steel drive shaft and provides reduced operational noise inservice.

While the above description has illustrated the invention as applied toa composite drive shaft, it is contemplated that the composite tubularmember can be used in other load transmitting applications.

Various modes of carrying out the invention are contemplated as beingwithin the scope of the following claims particularly pointing out anddistinctly claiming the subject matter which is regarded as theinvention.

I claim:
 1. A method of forming a composite torque-transmitting tubularstructure, comprising the steps of forming a metal yoke with a generallycylindrical sleeve, forming a rigid fiber reinforced resin tubularmember, forming a plurality of longitudinal circumferentially spacedribs on the outer surface of said sleeve, said ribs projecting radiallyoutward from said sleeve, forming a plurality of slots in an end of saidtubular member with said slots extending completely through the wall ofsaid tubular member and said slots opening at said end of the tubularmember with a tongue disposed between each pair of adjacent slots,moving the sleeve and the tubular member longitudinally of each other tobring the ribs into registry with the slots and to bring the tonguesinto contiguous overlapping relation with said sleeve, and applying aclamping force to overlapping portions of the sleeve and the tubularmember.
 2. The method of claim 1, and including the step of bonding theoverlapping portions of said sleeve and said tongues.
 3. The method ofclaim 1, wherein the steps of applying a clamping force compriseswinding a fibrous material impregnated with an uncured thermosettingresin around the overlapping portions of said sleeve and said tubularmember, and curing the resin.
 4. The method of claim 1, wherein saidribs are formed with a depth substantially equal to the thickness ofsaid tubular member.
 5. A method of forming a composite tubularstructure, comprising the steps of forming a metal yoke with a generallycylindrical sleeve, forming a fiber reinforced resin tubular member,forming a plurality of longitudinal circumferentially spaced ribs on theouter surface of said sleeve with the ribs projecting radially outwardof said sleeve, forming a plurality of longitudinal slots through an endof the tubular member with a tongue disposed between each pair ofadjacent slots and extending the slots to the end of the tubular memberand extending the slots through the wall of said tubular member, forminga recess between each adjacent pair of ribs in said sleeve and extendingeach recess at an acute angle to the longitudinal axis of said sleeve,moving the sleeve and tubular member longitudinally to bring the ribsinto registry with the slots and to insert the ends of the tongues intosaid recesses so that portions of said tubular member overlap saidsleeve, and applying a clamping force to the overlapping portions ofsaid tubular member and said sleeve.
 6. The method of claim 5, andincluding the steps of bonding the end portions of the tongues in saidrecesses.
 7. The method of claim 5, wherein the step of applying saidclamping force comprises winding a fibrous material impregnated with anuncured thermosetting resin about the overlapping portions of saidsleeve and said tubular member, and curing said thermosetting resin. 8.The method of claim 1, wherein the clamping force is applied tosubstantially the entire length of said overlapping portions of thesleeve and the tubular member.
 9. A method of forming a compositetorque-transmitting tubular structure, comprising the steps of forming ametal yoke with a generally cylindrical sleeve, forming a rigid fiberreinforced resin tubular member, forming a plurality of longitudinalcircumferentially spaced ribs on the outer surface of said sleeve, saidribs projecting radially outward from said sleeve, forming a pluralityof slots in an end of said tubular member with said slots extendingcompletely through the wall of said tubular member and said slotsopening at said end of the tubular member with a tongue disposed betweeneach pair of adjacent slots, moving the sleeve and the tubular memberlongitudinally of each other to bring the ribs into registry with theslots and to bring the tongues into contiguous overlapping relation withsaid sleeve, and applying an annular member over said ribs and saidtongues, said annular member having a longitudinal dimension at leastequal to the longitudinal dimension of said ribs.
 10. The method ofclaim 9, wherein said annular member comprises a metal band.